DJANGO: database dependent combobox remains empty. No items appear

I would like to create a combobox and display data from a database table (names of cities) inside it. The page is app1/home.html. I created the files and migrated the database, but the combobox remains empty. I don't know what I did wrong. I'm new to Django, sorry. I have read many tutorials and questions, but I have not solved.

How can I fix the combobox and correctly display City_Name in it? Thank you!!!

models.py

The table of database is called app1_select_city, while inside there is: id, and City_Name

from django.db import models 

class Select_City(models.Model): 
    Select_City= models.IntegerField() 

    def __str__(self):
        return self.Select_City

forms.py

from .models import Select_City
class TestForm(forms.Form):
    some_input = forms.CharField(max_length=100)
    city = forms.ModelChoiceField(queryset=Select_City.objects.all())

    class Meta:
        model = Select_City
        fields = ('City_Name',)

views.py

def combobox(request):
  query_results = Select_City.objects.all()

  if request.method =="POST":
        form = TestForm(request.POST)
  context = {'form': form, 'query_results': query_results}
  return render(request, 'app1/home.html', context)

home.html

<form method="post" novalidate>
  {% csrf_token %}
  <select id="sel_city" name="cities">
    <option value="{{ query_results }}">Select</option>
    {% for item in query_results  %}
    {% endfor %}
  </select>
</form>

I think the issue mainly pertains around your models.py & home.html

1. In models.py:

from django.db import models 
class Select_City(models.Model): 
    City_Name = models.CharField(max_length=100) 

    def __str__(self):
        return self.City_Name

    class Meta:
        db_table = 'app1_select_city'

The db_table attr makes sure that the model is linking to your app1_select_city table.
Moreover since you can directly return the City_Name, which is a char field not an int field, then you can reuse it in your forms.py as you wanted to.

2. In home.html, :
   To display the options in the combobox, you need to add an option element for each object in query_results queryset.
   This will create an option for each city in the queryset, with the id as the option value and the City_Name as the option label.

<form method="post" novalidate>
  {% csrf_token %}
<select id="sel_city" name="city">
    <option value="">Select a city</option>
    {% for city in query_results %}
        <option value="{{ city.id }}">{{ city.City_Name }}</option>
    {% endfor %}
</select>

Another quick edit:
You should init your form in views.py outside of the if-block, just so the form is always initialised
Add form = TestForm() outside the if-block

Ok, here is a lot to tackle.

Your model does not have a name field! It just has an IntegerField called Select_City which is the same name as the class. That is not good. Usually you want to write your model without underscores with Camelcase and your fields with underscores and no capital letters.

from django.db import models 

class City(models.Model): 
    name = models.CharField(max_length=30) 

    def __str__(self):
        # here you want to return the name
        # print function on an instance of this model then returns the name
        return self.name

After these changes you have to python manage.py makemigrations and python manage.py migrate. In case of issues I recommend deleting the database and migrations and then start again with mentioned commands.

forms.py. Why do you need input here? If you just want to select one of the models you just need the ModelChoiceField

from .models import City

class SelectCityForm(forms.Form):
    city = forms.ModelChoiceField(queryset=City.objects.all())

    class Meta:
        model = City
        fields = ('name')

Ok now when it comes to your view you want to separate its logic into a get and a post request. GET request when the user "goes" to your form when he is about to select a city. POST request after he selected a form when he pressed submit at the form. Then on POST request you want to display what you are confusingly referring to as "combobox". I call it city_detail. on GET you don't need to create the query_results here since this already happens within the form. Whereas on POST you want to filter the queryset for the selected city id.

def city_detail(request):
    form = CitySelectForm()
    object = None
    if request.method == "POST":
        form = CitySelectForm(request.POST)
        if form.is_valid():
            city_id = form.cleaned_data['city']
            object = City.objects.get(id=city_id)


    context = {'form': form, 'object': object}
    return render(request, 'app1/home.html', context)

Your template should show the form on GET and the City-Details (object) on POST

<form action="/url-to-city_detail-view/" method="post">
    {% csrf_token %}
    {{ form }}
    <input type="submit" value="Submit">
</form>
{% if object %}
Here you can embed data of your city such as the ID: {{ object.id }} or the Name: {{ object.name }}. Since you defined the __str__ method you can also
just put {{ object }} and it will give the name.
{% endif %}

All in all I have to say this is still not the cleanest approach, since you would normally "select" an Object of your database with parameters that you pass to the url.